Sugary drinks tinker with vital proteins in the brain

Glugging lots of sugary drinks won’t just make you fat, it might also lead to changes in the brain that have been linked to cancer and Alzheimer’s – at least in rats.

This finding comes from the first analysis of how sugary drinks affect proteins in the brain. It showed that 20 per cent of the proteins produced in a brain region related to decision-making were altered in rats that drank sugary drinks compared with those given water.

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But the effects of sugar-rich drinks on the brain have received much less attention. “For many people around the world, soft drinks are their sole source of liquid, or at least they provide a very high proportion of their daily calories”, says Jane Franklin at the behavioural neuropharmacology lab at Macquarie University in Sydney, Australia, who carried out the study. “We know that soft drinks are bad for the body, so it’s reasonable to assume that they aren’t doing anything good for your brain either”.

Hyperactive rats

To find out, Franklin and her colleague Jennifer Cornish gave 24 adult rats either water or a solution of water containing 10 per cent sugar – about the proportion you would find in an average can of soft drink – for 26 days.

For the following seven days, both groups were given only water. At the end of this time, the rats that had drunk the sugar drink were significantly more hyperactive – spending lots more time moving around – than the control group. “Hyperactivity is a physical sign that something unusual is happening in the brain,” says Franklin. It is probably a reflection of changes being made to return the system back to its pre-sugar state, after it had adjusted to allow it to function as normal during prolonged sugar consumption, she says.

To find out what was going on, the team looked at the rats’ orbital frontal cortex, the part of the brain that sits behind the eyes. An enzyme was used to snip proteins from this tissue into their constituent peptides. These fragments were then analysed using a mass spectrometer, which determines the peptides, and therefore the proteins, present. This was then compared to a database of the proteins you would expect to see in a healthy rat of this species.

Of the 1373 proteins identified in both sets of rats, 290 were altered in the rats that drank sugary drinks but not those that drank water. Some of the proteins were present in greater numbers, and some in fewer numbers than expected.

Unanticipated change

“This is a lot more change than we anticipated”, says Franklin, and is significantly more than the group saw in a similar analysis of caffeine in other brain areas.

While more work is needed to determine the exact effect of these changes, just under half of the altered proteins are known to be involved in the cellular function of the brain, including determining cellular lifespan, communication and DNA repair. Thirty per cent of the changed proteins are linked with conditions such as cancer, Alzheimer’s, Parkinson’s and schizophrenia.

“The results are telling us that sugar exposure has the potential to alter a lot of diverse biological processes and play a role in neurological disorders – much more than we expected,” says Franklin. “We can’t say from this work that these changes are causing the associated diseases, but it’s a warning that we need to look more closely at the link.”

The work was presented at this week’s conference of the Society for Neuroscience in San Diego, California.